Directional antenna system



Dec. 24, 1929. J MElSSNE 1,740,950

DIRECTIONAL ANTENNA SYSTEM Filed July 15. 1925 anoeutoz ga my/# 256720 Patented Dec. 24, 1929 UNITED STATES PAT ENT. OFFICE ALEXANDER MEISSNER, OF BERLIN, GERMANY, ASSIGNOR TO GESELLSGHAFT FIIR DRAHTLOSE TELEGRAPHIE M. B. E. OF BERLIN, GERMANY, A CORPORATION OF GERMANY DIRECTIONAL ANTENNA SYSTEM Application filed July 15, 1925, Serial No. 43,684, and in Germany July 25, 1924.

This invention is particularly adapted for the purpose of transmitting intelligence through space, especially by the use of short electromagnetic waves, as it is now well known that antennae capable of such transmission will produce strong radiation with the result that signals therefrom may be received at receiving stations at comparatively great distances away. In order to accomplish this object, aerials are located at a comparatively great distance from the ground, and are of considerable length or, on the other hand, grounded aerials of comparatively great vertical height are so excited or energized that they will oscillate on a wave length that is proportioned to the length of the antenna as one is to three-quarters or else as one is to a whole multiple of the wave length plus onequarter of the Wave length. Such a radiating antenna is usually attached at its upper end to a tall mast or tower from which it is insu lated and which tower is also insulated from the earth.

Where it is desired that a directional action of the radiation may be produced, refleeting auxiliary antennae are employed which may be arranged in a special form such as in a form having conductors in a parabolic surface, which surface may surround or properly enclose the transmitting or receiving antenna, as the case may be. Furthermore, refleeting actions are produced if conducting surfaces of bodies are located in the vicinity of the radiating or transmitting antenna above mentioned.

The object of the present invention is to utilize the tower carrying the radiating aerial in such a manner that it acts as a reflector for the short waves emitted by said transmitting aerial. Such towers are obviously made of conductive material, such as steel, and are capable of having a natural period of oscillation. In order to control the period of oscillation, the said mast or tower can be given the requisite shape to embody the electrical constants which will cause it to oscillate at the desired period of oscillation or wave length. In order to produce a definite directive efiect a certain angle of phase displacement must exist between the oscillations of the aerial and the oscillations of the refleeting means which, in the present instance,

is the supporting tower. This phase displacement, under certain conditions, requires means for adjusting the period of oscillation of the tower to correspond with and effect the necessary relation with the oscillations induced therein by the transmitting aerial. Ac cording to the present invention such tuning means are provided as a part of the tower structure or are connected therewith and with i a ground connection preferably through a variable reactance.

One form of the invention is illustrated in the accompanying drawing in which the letter A indicates the radiating aerial which} as indicated by the dotted line, has a length such that it oscillates on a wave length which is one and one-quarter the length of the transmitting wave. The aerial A is attached to the top of the supporting tower or mast M frontwhich it is insulated as indicated. This mast is constructed of conductive material and at the bottom rests on an insulator J. For the purpose of tuning said supporting tower to the proper period it is grounded through a reactance W consisting of an induct-ion coil and condenser, said reactance being made variable as indicated.

Having thus described this form of my in vention what I claim and desire to protect by Letters Patent is:

1. A directional antenna system comprising an aerial, a conductive support therefor, 85 a tunable circuit between said support and: the ground for proportioning the electrical characteristics of said support so as to reflect the oscillations induced therein by the oscillations generated in the aerial at a desired 90 Wave length, whereby the aerial is given a directional characteristic.

2. A directional antenna system comprising an aerial, a conductive support therefor, said support being insulated from said aerial and from the ground and tuning means forming a path for high frequency currents between said support and the ground, whereby the aerial, by virtue of absorption and reflection by the support, of electromagnetic energy radiated from the aerial, is given a directional characteristic.

Signed at Berlin, Germany, this 23rd day of June, 1925.

1 ALEXANDER MEISSNER. 

